Issue 9, 2020

Super-coercive electric field hysteresis in ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(iii)

Abstract

Ionic plastic crystals are part of an emerging class of hybrid organic–inorganic ferroelectrics. The combination of low dielectric constants (<20), strong piezoelectric coefficients (>100 pC N−1) and low temperature synthesis make ferroelectric plastic crystals strong candidates for sensing and energy harvesting applications so more research of the electrical properties, such as dielectric loss and super-coercive hysteresis is needed. Tetramethylammonium bromotrichloroferrate(III) was studied as a prototypical material and a non-centrosymmetric orthorhombic Amm2 structure was confirmed by X-ray diffraction at room temperature. The relative permittivity was below 20 at high frequencies (105 Hz) but high dielectric losses at frequencies <103 Hz caused the permittivity to increase. The bulk material showed super-coercive hysteresis with remanent polarizations of 3.8 μC cm−2 and peak-to-peak strains of 0.046%. The coercive field and peak-to-peak strain exhibited frequency dependence, reducing from >80 to 30 kV cm−1 and 0.046 to 0.017% respectively between 100 and 0.1 Hz. At 100 Hz the material exhibited a strong asymmetric hysteresis that was reversible depending on the electric field direction. The observed behavior was consistent with a defect pinning model of ferroelectric switching behavior and thus some likely point defect species were proposed and thought to result from solution non-stoichiometry or residual moisture and solvent.

Graphical abstract: Super-coercive electric field hysteresis in ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(iii)

Article information

Article type
Paper
Submitted
18 Dec 2019
Accepted
28 Jan 2020
First published
31 Jan 2020

J. Mater. Chem. C, 2020,8, 3206-3216

Super-coercive electric field hysteresis in ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(III)

J. Walker, R. Miranti, S. L. Skjærvø, T. Rojac, T. Grande and M. Einarsrud, J. Mater. Chem. C, 2020, 8, 3206 DOI: 10.1039/C9TC06918F

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